A standard central motor-vehicle lock system has a plurality of door latches on the individual doors, hatches, trunk lids, and the like that are each operable by a respective power actuator and also by a manual mechanism. The power actuator can include a hydraulic, pneumatic, or electric motor, and the manual mechanism is almost always a lever linkage.
In a standard system such as described in U.S. Pat. No. 4,342,209 each door latch has a locking lever displaceable between a pair of end positions corresponding to locked and unlocked conditions of the respective door. This lever is connected on the one side via a rod to the inside unlocking button in the case of a door and on the other side via another rod to the power actuator which is mounted in the door at some remove from the latch. Thus either the knob or the actuator can be operated to lock or unlock the door.
As described in commonly owned U.S. Pat. No. 5,056,343 issued 15 Oct. 1991 the actuator for such a lock system has an electric motor whose output shaft carries a drive pinion that is in continuous mesh with a larger-diameter input gear carried on a threaded spindle in turn carrying a nut. This nut is coupled via a system of deflectable arms to the actuating element. Thus the latch can be moved manually or by the motor between the locked and unlocked position. When moved manually from the locked to the unlocked position, it is necessary for the motor to be operated to move the nut back into the corresponding position before motor-powered operation can resume.
Commonly owned U.S. Pat. Nos. 5,149,156 and 5,441,315 describe a system wherein a support pivotal in the housing carries a pair of coupling gears in mesh with and flanking the output gear of the motor actuator. The support is rockable from a central position in which neither of the coupling gears meshes with the input gear into a pair of end positions in each of which a respective one of the coupling gears meshes with the input gear and couples same to the output gear. The support is biased into the central position with a relatively small force such that on rotation of the input gear in either direction the biasing force is overcome and the support is rocked in the same direction into the respective end position.
With this system, therefore, there is no need to reverse drive the motor so the link parts can reassume the proper position if after power actuation the door lock is operated manually. The power actuator can pick up right where it left off. Such a system requires that two extra gears be built into the system and a housing including journals for them be provided.